package com.example.io;

import org.junit.Test;

import java.io.*;

/**
 * @author readpage
 * @create 2022-10-15 11:23
 *
 * 处理流之一: 缓冲流的使用
 * 1.缓冲流:
 * BufferedInputStream
 * BufferedOutputStream
 * BufferedReader
 * BufferedWriter
 *
 * 2.作用: 提高流的读取、写入的速度
 *      提高读写速度的原因: 内部提供了一个缓冲区
 *
 * 3.处理流，就是"套接"在已有的流的基础上。
 */
public class BufferedTest {


    //实现文件复制的方法
    public void copyFileWithBuffered(String srcPath, String destPath) {
        FileInputStream fis = null;
        FileOutputStream fos = null;
        BufferedInputStream bis = null;
        BufferedOutputStream bos = null;
        try {
            //1.创建文件
            File srcFile = new File(srcPath);
            File destFile = new File(destPath);
            //2.创建流
            //2.1 创建节点流
            fis = new FileInputStream(srcFile);
            fos = new FileOutputStream(destFile);
            //2.2 创建缓冲流
            bis = new BufferedInputStream(fis);
            bos = new BufferedOutputStream(fos);

            //3.复制的细节: 读取、写入
            byte[] buffer = new byte[100];
            int len;
            while ((len = bis.read(buffer)) != -1) {
                bos.write(buffer, 0, len);
            }
        } catch (IOException e) {
            throw new RuntimeException(e);
        } finally {
            //4.资源关闭
            //要求先关闭外层的流，再关闭内存的流
            if (bos != null) {
                try {
                    bos.close();
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            if (bis != null) {
                try {
                    bis.close();
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
        }

        //说明: 关闭外层流的同时，内层流也会自动的进行关闭。关于内层流的关闭，可以省略。
//        fos.close();
//        fis.close();
    }

    @Test
    public void testCopyFile() {
        long start = System.currentTimeMillis();

        String srcPath = "E:\\GY_NEW.zip";
        String destPath = "E:\\tmp\\GY_NEW4.zip";
        copyFileWithBuffered(srcPath, destPath);

        long end = System.currentTimeMillis();

        System.out.println("复制操作花费的时间为: " + (end - start));
    }

    /**
     * 使用BufferedReader 和 BufferedWriter实现文本文件的复制
     */
    @Test
    public void testBufferedReaderBufferedWriter() {
        BufferedReader br = null;
        BufferedWriter bw = null;
        try {
            br = new BufferedReader(new FileReader(new File("hello.txt")));
            bw = new BufferedWriter(new FileWriter(new File("hello3.txt")));

//            //读写操作
//            //方式一
//            char[] cbuf = new char[1024];
//            int len;
//            while ((len = br.read(cbuf)) != -1) {
//                bw.write(cbuf, 0, len);
//            }

            //方式二： 使用String
            String data;
            while ((data = br.readLine()) != null) {
                bw.write(data); //data中不包含换行
                bw.newLine(); //提供换行的操作
            }

        } catch (IOException e) {
            throw new RuntimeException(e);
        } finally {
            if (bw != null) {
                try {
                    bw.close();
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            if (br != null) {
                try {
                    br.close();
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
        }
    }
}
